Mammalian cytokine, IL-11

ABSTRACT

A novel mammalian cytokine, IL-11, and processes for producing it are disclosed. IL-11 may be used in pharmaceutical preparations for stimulating and/or enhancing cells involved in the immune response and cells involved in the proper functioning of the hematopoietic system.

CROSS-REFERENCE TO RELATED U.S. APPLICATIONS

This is a continuation-in-part of U.S. Ser. No. 07/526,474, filed May21, 1990, and issued as U.S. Pat. No. 5,215,895 on Jun. 1, 1993; whichin turn is a continuation-in-part application of U.S. Ser. No.07/441,100, filed Nov. 22, 1989, now abandoned. U.S. Ser. No. 08/017,522(filed Feb. 11, 1993) and issued Dec. 6, 1994 as U.S. Pat. No. 5,371,193is a divisional of U.S. Pat. No. 5,215,895.

The present invention relates to a novel cytokine that stimulates thefunction of cells of the immune and hematopoietic systems, and toprocesses for obtaining the factor and producing it by recombinantgenetic engineering techniques.

BACKGROUND OF THE INVENTION

A growing family of regulatory proteins that deliver signals betweencells of the immune system has been identified. These regulatorymolecules are known as cytokines. Many of the cytokines have been foundto control the growth and development, as well as the biologicalactivities of cells of the hematopoietic and immune systems. Theseregulatory molecules include all of the colony-stimulating factors(e.g., GM-CSF, G-CSF, M-CSF, and multi CSF or interleukin-3), theinterleukins (IL-1 through IL-9), the interferons (alpha, beta andgamma), the tumor necrosis factors (alpha and beta), erythropoietin,macrophage inhibitory proteins, the tumor growth factors and leukemiainhibitory factor (LIF). These cytokines exhibit a wide range ofbiological activities with target cells from bone marrow, peripheralblood, fetal liver, and other lymphoid or hematopoietic organs. See,e.g., F. R. Balkwill and F. Burke, Immunology Today, 10(9):299 (1989);G. Wong and S. Clark, Immunology Today, 9(5):137 (1988); and S. C. Clarkand R. Kamen, Science, 236:1229-1237 (1987).

The biochemical and biological identification and characterization ofcertain cytokines was hampered by the small quantities of the naturallyoccurring factors available from natural sources, e.g., blood and urine.Many of the cytokines have recently been molecularly cloned,heterologously expressed and purified to homogeneity. Several of thesepurified factors have been found to demonstrate regulatory effects onthe hematopoietic and immune systems in vivo, including GM-CSF, M-CSF,G-CSF, IL-1, IL-2, IL-3, IL-6, IL-7, TNF, the interferons anderythropoietin.

There remains a need in the art for additional proteins purified fromtheir natural sources or otherwise produced in homogeneous form, whichare capable of stimulating or enhancing immune responsiveness andhematopoietic cell development, which are suitable for pharmaceuticaluse.

SUMMARY OF THE INVENTION

In one aspect the present invention provides a novel mammalian cytokine,called IL-11, which is substantially free from other mammalian proteins.This protein may be produced by recombinant genetic engineeringtechniques. It may also be purified from cell sources producing thefactor naturally or upon induction with other factors. IL-11 may also besynthesized by chemical techniques, or a combination of the above-listedtechniques.

Active, mature mammalian IL-11 is an approximately 178 amino acidprotein, characterized by an apparent molecular weight of approximately20 kd, as determined by analyzing ³⁵ S methionine labelled supernatantfluid derived from IL-11 cDNA transfected COS-1 cells on sodiumdodecylsulfate polyacrylamide gel electrophoresis. The calculatedmolecular weight for the mature protein is also approximately 20 kd.

The IL-11 protein of this invention has displayed biological activitiesin various assays, which indicate its role as a general stimulator of avariety of hematopoietic and immune functions. The IL-11 protein of thisinvention demonstrates proliferative activity in an IL-6 dependent mouseplasmacytoma cell line, T1165. IL-11 has also demonstrated inpreliminary assays, the ability to stimulate, either directly orindirectly, the maturation of B cells. Specifically, IL-11 is believedto stimulate the T cell dependent development of B cells. It has furtherdemonstrated synergy with IL-3 in an assay stimulating megakaryocyteproliferation, but may act on other lineages as well.

Another aspect of the present invention is a DNA sequence that encodesthe expression of a mammalian IL-11 protein. This DNA sequence mayinclude an isolated DNA sequence that encodes the expression of amammalian IL-11 protein as described above. The DNA sequence coding foractive IL-11 is characterized as comprising the same or substantiallythe same nucleotide sequence in Table I or fragments thereof. This DNAsequence may include 5' and 3' mammalian non-coding sequences flankingthe IL-11 coding sequence. The DNA sequence may also encode an aminoterminal signal peptide. Table I illustrates these non-coding 5' and 3'flanking sequences and a signal sequence of mammalian IL-11 isolatedfrom the primate cell line PU34 and expressed in COS-1 cells.

It is understood that the DNA sequence of this invention may, however,exclude some or all of these flanking or signal sequences. Moreover theDNA sequence of the present invention which encodes a biologicallyactive mammalian IL-11 protein may also comprise DNA capable ofhybridizing under appropriate conditions, or which would be capable ofhybridizing under said conditions, but for the degeneracy of the geneticcode, to an isolated DNA sequence of Table I. Thus, the DNA sequence ofthis invention may include or contain modifications in the non-codingsequences, signal sequences or coding sequences based on allelicvariation, species variation or deliberate modification.

Also provided by the present invention is a recombinant DNA moleculecomprising vector DNA and a DNA sequence encoding mammalian IL-11. TheDNA molecule provides the IL-11 DNA in operative association with aregulatory sequence capable of directing the replication and expressionof IL-11 in a selected host cell. Host cells transformed with such DNAmolecules for use in expressing recombinant IL-11 protein are alsoprovided by the present invention.

The DNA molecules and transformed cells of the invention are employed inanother aspect, a novel process for producing recombinant mammalianIL-11 protein, or peptide fragments thereof. In this process a cell linetransformed with a DNA sequence encoding expression of IL-11 protein ora fragment thereof (or a recombinant DNA molecule as described above) inoperative association with a suitable regulatory or expression controlsequence capable of controlling expression of the protein is culturedunder appropriate conditions permitting expression of the recombinantDNA. The expressed IL-11 protein is then harvested from the host cell orculture medium by suitable conventional means. This claimed process mayemploy a number of known cells as host cells for expression of theprotein. Presently preferred cell lines for producing IL-11 aremammalian cell lines and bacterial cells.

Another aspect of this invention provides pharmaceutical compositionscontaining a therapeutically effective amount of mammalian IL-11 or ofone or more biologically active peptide fragments thereof. Theseproteins or peptide fragments may be presented in a pharmaceuticallyacceptable vehicle. These pharmaceutical compositions may be employed,alone or in combination with other suitable pharmaceutical agents, inmethods for treating disease states characterized by a deficiency in thenumber or level of activity of hematopoietic cells. Pharmaceuticalcompositions containing IL-11 may be also be employed for the treatmentof disorders of the immune system, such as immunodeficiencies.

IL-11 containing compositions may be used to stimulate megakaryocytegrowth and differentiation in synergy with IL-3. Additional areas of useare in platelet formation, acquired chemotherapeutic or bone marrowrelated thrombocytopenia. IL-11 is also likely to operate as an effectormolecule to improve the function of other cytokines. IL-11 compositionsmay also be useful in directly or indirectly stimulating the productionor function of B cells. Thus IL-11 compositions may be employed intherapies for cancer, the treatment of infections, acceleration of woundhealing and in stimulating the immune system in general. IL-11 may alsobe used in potentiating the immune response to certain antigens,particularly vaccines.

A further aspect of the invention, therefore, is a method for treatingthese and/or other pathological states by administering to a patient atherapeutically effective amount of IL-11 or a peptide fragment thereofin a suitable pharmaceutical carrier. These therapeutic methods mayinclude administering simultaneously or sequentially with IL-11 or apeptide fragment thereof an effective amount of at least one othercytokine, hematopoietin, interleukin, growth factor, or antibody.

Still another aspect of the present invention are antibodies directedagainst mammalian IL-11 or a peptide thereof. As part of this aspect,therefore, the invention claims cell lines capable of secreting suchantibodies and methods for their production.

Other aspects and advantages of the present invention are describedfurther in the following detailed description of preferred embodimentsof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically depicts the enhancement of the development of murineNP-reactive B cells by pC1R6-transfected cos-1 cell conditioned mediumin the murine plaque-forming assay.

FIG. 2 graphically depicts the enhancement of the development ofIL-3-dependent murine megakaryocyte colonies by pC1R6-transfected cos-1cell conditioned medium in the murine fibrin clot assay.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a biologically active mammalian cytokine,IL-11, in a form substantially free from association with othermammalian proteins and proteinaceous materials. This protein can beproduced via recombinant techniques to enable large quantity productionof pure, active IL-11 useful for therapeutic applications.Alternatively, this protein may be obtained as a homogeneous proteinpurified from a mammalian cell line secreting or expressing it. FurtherIL-11 or active fragments thereof may be chemically synthesized.

Mammalian IL-11 was initially isolated from a primate cell linedeveloped by placing bone marrow cells from a healthy macaque monkey inlong term culture and infecting them with the retrovirus U19-5 Dr. RogerCone, Tufts Medical School!. After incubation with the appropriateantibiotic, a live cell line designated PU34 was selected for its growthcharacteristics and induced with IL-1 alpha expressed in E. coli.Conditioned medium showed activity in a proliferation assay with IL-6dependent mouse plasmacytoma cells in the presence of neutralizingantibody to IL-6. A cDNA library was prepared from IL-1-stimulated(2u/ml IL-1 for 24 hours) PU34 cell mRNA according to the expressioncloning method previously described in, e.g., G. G. Wong et al, Science,228:810-815 (1985); Y. C. Yang et al, Cell, 47:3-10 (1986); and A. E.Namen et al, Nature, 333:571-573 (1988).

The library was constructed in an expression vector which permits theexpression of cDNA inserts in mammalian cells, e.g. COS-1 cells.Screening of the library was performed by transfecting COS-1 cells with5 μg of DNA prepared from pools of 200-500 cDNA clones. By assaying thesupernatant fluid for activity in the T1165 assay, cDNA clonesexpressing IL-11 activity were identified.

An isolated clone having T1165 activity was called pPU34-TRA (alsocalled pC1R6) and was sequenced. Table I illustrates the cDNA sequenceand the amino acid sequence (single letter code) of both the primate andhuman clones of the IL-11 polypeptide. The nucleotide sequence fromposition 1-721 for the primate sequence was obtained from pC1R6. Theremainder, from nucleotides 721-1102 was sequenced from a second primatecDNA isolated by hybridization with pC1R6. A human cDNA encoding theplasmacytoma stimulatory activity of IL-11 was isolated from a cDNAlibrary prepared from the human lung cell line, MRC5 described by Jacobset al, Nature, 227:43 (1970) by direct hybridization with the insertfrom pPU34-TRA (pC1R6). The differences found in the human IL-11nucleotide sequence are indicated in Table I above the primate sequenceand the resulting changes in amino acid sequences are indicated belowthe appropriate amino acid in the primate sequence.

The primate nucleotide sequence comprises 1100 base pairs. The primatesequence contains a 5' non-coding sequence of 72 base pairs. Thesequence of Table I also shows a 3' non-coding sequence of 431 bases.The human nucleotide sequence similarly contained a single long readingframe of 597 nucleotides.

Both the primate and the human sequences are characterized by a singlelong open reading frame predicting an unprocessed 199 amino acidpolypeptide which begins at primate nucleotide position 73 in Table I.The first 21 amino acids from positions (1) Met to position (21) Ala inthe predicted amino acid sequence of IL-11 from both the primate andhuman clones contain a stretch of hydrophobic amino acids that resemblesa conventional mammalian secretory leader sequence D. Perlman et al, J.Mol. Biol., 167:391-409 (1983)!. The N-terminal of the mature IL-11protein (underlined in Table I) and consists of the amino acid sequencePRO-GLY-PRO-PRO-PRO-GLY. The protein is first synthesized as a precursorof 199 amino acids which gets proteolytically cleaved betweennucleotides #134-135, to yield a mature 178 amino acid polypeptidebeginning with the sequence Pro-Gly at amino acid positions 22-23 andterminating after amino acid position 199 at the TGA termination tripletat nucleotide positions 671-672. The calculated molecular mass of themature protein correspond well with the apparent molecular weight of anovel protein band revealed by SDS-PAGE (reducing conditions) ofsupernatant fluid derived from IL-11 cDNA transfected COS-1 cells, thatis, approximately 20 kd in both cases.

                                      TABLE I                                     __________________________________________________________________________    Primate and Human IL-11 sequence, 5'-3'                                       Differences between human and primate sequence are indicated by bases         above primate                                                                 nucleotide sequence and amino acids below primate amino acid                  __________________________________________________________________________    sequence.                                                                     GGGAAGGTGGAAGGGTTAAAGGCCCCCGGCTCCCTGCCCC40                                     ##STR1##                                                                      ##STR2##                                                                      ##STR3##                                                                      ##STR4##                                                                      ##STR5##                                                                      ##STR6##                                                                      ##STR7##                                                                      ##STR8##                                                                      ##STR9##                                                                      ##STR10##                                                                     ##STR11##                                                                     ##STR12##                                                                     ##STR13##                                                                     ##STR14##                                                                     ##STR15##                                                                     ##STR16##                                                                     ##STR17##                                                                    AAAGCCACATCTTATTTATTTATTTATTTCGGTACTGGGG742                                   GCGAAACAGCCAGGTGATCCCCCTGCCTTTAGCTCCCCCT782                                   AGTTAGAGACAGTCCTTCCGTGAGGCTGGGGGGCATCTGT822                                   GCCTTATTTATACTTATTTATTTCAGGAGCGGGGGTGGGC862                                   TCCTGGGTCCCCGAGGAGGAGGGAGCTGGGGTCCCGGATT902                                   CTTGTGTCCACAGACTTCTGCCCTGGCTCCTCCCCCTCGA942                                   GGCCTGGGCAGGAATACATACTATTTATTTAAGCAATTAC982                                   TTTTCATGTTGGGGTGGGGAGGGAGGGGAAAGGGAAGCCT1022                                  GGGTTTTTGTACAAAAATGTGAGAAACCTTTGTGAGACGG1062                                  AGAACAAGGAATTAAATGTGTCATACATAAAAAAAAAA1100                                    __________________________________________________________________________

The nucleotide sequence of IL-11 cDNA has been compared with thenucleotide sequences recorded in Genbank. No significant similarities innucleotide sequence were found with the published DNA sequences of otherproteins. Only mild homology was found between the leader sequence ofIL-11 and those of gamma interferon and IL-6. No significant homologywas found between the coding sequence of IL-11 and any other publishedpolypeptide sequence.

Additionally, as described in more detail in Example 11, IL-11 is asynergistic factor for IL-3-dependent proliferation of primitiveprogenitors. A result of the synergism is the shortening of the G_(o)period of the stem cells. In at least one culture system, IL-11, likeIL-6, acts synergistically with IL-3 in support of megakaryocyte colonyformation S. R. Paul et al, Proc. Natl. Acad. Sci. U.S.A., 87:7512-7516(1990)!. Thus, it appears that IL-11, as well as G-CSF and IL-6,interacts with early and late hempoietic lineages. However, in constrastto IL-6, which is also such a synergistic factor, IL-11 preferentiallystimulates only macrophage proliferation in secondary cultures of pooledblast cells. Thus, IL-11 appears to be distinct from other knownlymphokines, factors and proteins. IL-11 is also implicated in playing arole within the lymphoid lineages, resulting in stimulation of multiplearms of the defense system. Thus, IL-11 is expected to be useful in themanipulation of stem cells for both experimental and clinical purposes.

The biological activity of the mammalian IL-11 encoded by this sequencewas detected in the functional polypeptides produced by mammalian cellstransfected with the cloned sequence under the control of appropriateexpression control sequences. The cloned primate sequence in plasmidpPU34-TRA (pC1R6) as reported in Table I was deposited with the AmericanType Culture Collection, 12301 Parklawn Drive, Rockville, Md. on Nov.14, 1989 under ATCC No. 68172. The cloned human sequence, illustrated inTable I by the modifications from the primate sequence on both thenucleotide and amino acid levels, was deposited with the American TypeCulture Collection, 12301 Parklawn Drive, Rockville, Md. on Mar. 30,1990 under ATCC No. 68284.

The IL-11 polypeptide is active in the T1165 assay, described below. Ininitial studies, IL-11 was found to significantly enhance the formationof immunoglobulin-secreting B cells in a standard murine spleen cellplaque formation assay, even at final dilutions as high as 1:500. Thissystem measures the development of B cells in culture that respond to aspecific immunogen, 4-hydroxy-3-nitrophenyl-acetyl-modified horse redblood cells (NP-HRBC) in the context of the normal cellular constituentsof the spleen. Thy 1 complement-mediated depletion of T cells from thespleen cell cultures resulted in complete abrogation of the response,demonstrating that the increase in NP-responding B cells, even in thepresence of the primate IL-11, depends at least in part on the presenceof T cells. The activity of IL-11 is therefore not attributable to adirect B cell mitogenic effect because B cell mitogens, such aslipopolysaccharide, stimulate the formation of NP-specific plaqueforming cells in the absence of T cells. Thus IL-11 may regulate theproliferation, differentiation and activation of T and B lymphocytes.

Analysis of the effects of the IL-11 in a variety of hematopoieticculture systems revealed striking effects on megakaryocyte development.With murine bone marrow cells as targets, IL-11 had little effect alone,but stimulated by threefold megakaryocyte colony formation supported byIL-3. CFU-Meg formation with IL-3 and IL-11 exceeded that of aplasticcanine serum which is used as a positive control.

The IL-11 polypeptides provided herein also include factors encoded bysequences similar to that of recombinant IL-11 in Table I, but intowhich modifications are naturally provided or deliberately engineered.Thus the present invention also encompasses these novel DNA sequences,free of association with DNA sequences encoding other primate proteins,and coding on expression for IL-11 polypeptides. These DNA sequencesinclude sequences the same or substantially the same as theabove-identified DNA sequence and fragments thereof, and those sequenceswhich hybridize under stringent hybridization conditions see, T.Maniatis et al, Molecular Cloning (A Laboratory Manual), Cold SpringHarbor Laboratory (1982), pages 387 to 389! to the DNA sequence of TableI. An example of one such stringent hybridization condition ishybridization at 4XSSC at 65° C., followed by a washing in 0.1XSSC at65° C. for an hour. Alternatively an exemplary stringent hybridizationcondition is 50% formamide, 4XSSC at 42° C.

DNA sequences which hybridize to the sequences for IL-11 or activefragments thereof under relaxed hybridization conditions and which codeon expression for IL-11 peptides having IL-11 biological properties alsoencode novel IL-11 polypeptides. Examples of such non-stringenthybridization conditions are 4XSSC at 50° C. or hybridization with30-40% formamide at 42° C. For example, a DNA sequence which sharesregions of significant homology with the sequences of IL-11 and encodesa protein having one or more IL-11 biological properties clearly encodesa IL-11 polypeptide even if such a DNA sequence would not stringentlyhybridize to the IL-11 sequence of Table I or to fragments thereofencoding peptides with IL-11 activity.

Similarly, DNA sequences which code for IL-11 polypeptides but whichdiffer in codon sequence due to the degeneracies of the genetic code arealso encompassed by this invention. Allelic variations(naturally-occurring base changes in the species population which may ormay not result in an amino acid change) in DNA sequences encoding theIL-11 protein sequences and peptide fragments thereof evidencing IL-11biological activity are also included in the present invention as wellas analogs or derivatives thereof. Other variations in the DNA sequenceof IL-11 which are caused by point mutations or by induced modificationsto enhance certain characteristics of the IL-11 protein, such as thebiological activity, half-life or production of the polypeptides encodedthereby are also encompassed in the invention.

In addition to the use of the cDNA sequence above in recombinanttechniques, IL-11 polypeptides of this invention may also be produced byknown conventional chemical synthesis. Methods for constructing thepolypeptides of the present invention by synthetic means are known tothose of skill in the art. The synthetically-constructed IL-11polypeptide sequences or fragments thereof which duplicate or partiallyduplicate continuous sequences of the amino acid residues of Table I arealso part of this invention. The synthetically-constructed IL-11polypeptide sequences, by virtue of sharing primary, secondary, ortertiary structural and conformational characteristics with naturalIL-11 polypeptides may possess IL-11 biological properties in commontherewith. Thus, they may be employed as biologically active orimmunological substitutes for natural, purified IL-11 polypeptides intherapeutic and immunological processes.

Modifications in the protein, peptide or DNA sequences of IL-11 oractive fragments thereof can be made by one skilled in the art usingknown techniques. Modifications of interest in the IL-11 sequences mayinclude the replacement, insertion or deletion of one or more selectedamino acid residues in the coding sequences. Mutagenic techniques forsuch replacement, insertion or deletion are well known to one skilled inthe art. See, e.g., U.S. Pat. No. 4,518,584.!

Other specific mutations of the sequences of the IL-11 polypeptidedescribed herein may involve, e.g., the insertion of one or moreglycosylation sites. An asparagine-linked glycosylation recognition sitecan be inserted into the sequence by the deletion, substitution oraddition of amino acids into the peptide sequence or nucleotides intothe DNA sequence. Such changes may be made at any site of the moleculethat is modified by addition of O-linked carbohydrate or at other sitesin the molecule. Expression of such altered nucleotide or peptidesequences produces variants which may be glycosylated at those sites andwhich may have altered or improved pharmacological or biologicproperties.

Additional analogs and derivatives of the sequence of IL-11 which wouldbe expected to retain IL-11 activity in whole or in part may also beeasily made by one of skill in the art given the disclosures herein. Onesuch modification may be the attachment of polyethylene glycol (PEG)onto existing lysine residues in the IL-11 sequence or the insertion ofone or more lysine residues or other amino acid residues that can reactwith PEG or PEG derivatives into the sequence by conventional techniquesto enable the attachment of PEG moieties. Such modifications arebelieved to be encompassed by this invention.

The present invention also provides a method for producing IL-11polypeptides or active fragments thereof. One method of the presentinvention involves introducing the cDNA encoding an IL-11 polypeptideinto an expression vector to make an expression system for IL-11. Aselected host cell is transformed with the vector and cultured. Themethod of this present invention therefore comprises culturing asuitable cell or cell line, which has been transformed with a DNAsequence coding on expression for an IL-11 polypeptide or a fragmentthereof under the control of known regulatory sequences. The expressedfactor is then recovered, isolated and purified from the culture medium(or from the cell, if expressed intracellularly) by appropriate meansknown to one of skill in the art.

Suitable cells or cell lines for this method may be mammalian cells,such as Chinese hamster ovary cells (CHO) or 3T3 cells. The selection ofsuitable mammalian host cells and methods for transformation, culture,amplification, screening and product production and purification areknown in the art. See, e.g., Gething and Sambrook, Nature, 293:620-625(1981), or alternatively, Kaufman et al, Mol. Cell. Biol.,4(7):1750-1759 (1985) or Howley et al, U.S. Pat. No. 4,419,446. Othersuitable mammalian cell lines are the monkey COS-1 cell line and theCV-1 cell line. Further exemplary mammalian host cells includeparticularly primate cell lines and rodent cell lines, includingtransformed cell lines. Normal diploid cells, cell strains derived fromin vitro culture of primary tissue, as well as primary explants, arealso suitable. Candidate cells may be genotypically deficient in theselection gene, or may contain a dominantly acting selection gene. Othersuitable mammalian cell lines include but are not limited to, HeLa,mouse L-929 cells, 3T3 lines derived from Swiss, Balb-c or NIH mice, BHKor HaK hamster cell lines.

Similarly useful as host cells suitable for the present invention arebacterial cells. For example, the various strains of E. coli (e.g.,HB101, and MC1061) are well-known as host cells in the field ofbiotechnology. Various strains of B. subtilis, Pseudomonas, otherbacilli and the like may also be employed in this method.

Many strains of yeast cells known to those skilled in the art are alsoavailable as host cells for expression of the polypeptides of thepresent invention. Additionally, where desired, insect cells may beutilized as host cells in the method of the present invention. See, e.g.Miller et al, Genetic Engineering, 8:277-298 (Plenum Press 1986) andreferences cited therein.

The present invention also provides recombinant DNA molecules, orvectors, for use in the method of expression of novel IL-11polypeptides. These vectors contain the novel isolated DNA sequenceswhich code for IL-11 polypeptides of the invention. Alternatively,vectors incorporating modified sequences as described above are alsoembodiments of the present invention and useful in the production ofIL-11 polypeptides. The vector employed in the method also containsselected regulatory sequences in operative association with the DNAcoding sequences of the invention and capable of directing thereplication and expression thereof in selected host cells.

The vector used in the examples below is pXM Y. C. Yang et al, Cell,47:3-10 (1986)!. The mammalian cell expression vectors described hereinmay be synthesized by techniques well known to those skilled in thisart. The components of the vectors, e.g. replicons, selection genes,enhancers, promoters, and the like, may be obtained from natural sourcesor synthesized by known procedures. See, Kaufman et al, J. Mol. Biol.,159:511-521 (1982); and Kaufman, Proc. Natl. Acad. Sci. USA, 82:689-693(1985). Alternatively, the vector DNA may include all or part of thebovine papilloma virus genome Lusky et al, Cell, 36:391-401 (1984)! andbe carried in cell lines such as C127 mouse cells as a stable episomalelement. The transformation of these vectors into appropriate host cellscan result in expression of the IL-11 polypeptides.

Other appropriate expression vectors of which numerous types are knownin the art for mammalian, insect, yeast, fungal and bacterial expressioncan also be used for this purpose.

IL-11, purified to homogeneity from cell sources or producedrecombinantly or synthetically, may be used in a pharmaceuticalpreparation or formulation to treat immune deficiencies or disorders.IL-11 may also be employed to treat deficiencies in hematopoieticprogenitor or stem cells, or disorders relating thereto. IL-11compositions may be employed in methods for treating cancer and otherpathological states resulting from disease, exposure to radiation ordrugs, and including for example, leukopenia, bacterial and vitalinfections, anemia, B cell or T cell deficiencies, including immune cellor hematopoietic cell deficiency following a bone marrowtransplantation. IL-11 may also be used to potentiate the immuneresponse to a variety of vaccines creating longer lasting and moreeffective immunity. As mentioned previously, IL-11 compositions may beemployed to stimulate development of B cells, and megakaryocytes.Therapeutic treatment of such disease states with these IL-11polypeptide compositions may avoid undesirable side effects caused bytreatment with presently available drugs.

The polypeptides of the present invention may also be employed, alone orin combination with other cytokines, hematopoietins, interleukins,growth factors or antibodies in the treatment of the above-identifiedconditions.

The present invention also provides methods and therapeutic compositionsfor treating the conditions referred to above. Such compositionscomprise a therapeutically effective amount of an IL-11 polypeptide ofthe present invention in admixture with a pharmaceutically acceptablecarrier. This composition can be systematically administeredparenterally. Alternatively, the composition may be administeredintravenously. If desirable, the composition may be administeredsubcutaneously or topically, e.g., at the site of a wound. Whensystematically administered, the therapeutic composition for use in thisinvention is in the form of a pyrogen-free, parenterally acceptableaqueous solution. The preparation of such a pharmaceutically acceptableprotein solution, having due regard to pH, isotonicity, stability andthe like, is within the skill of the art.

The dosage regimen involved in a method for treating the above-describedconditions will be determined by the attending physician consideringvarious factors which modify the action of drugs, e.g. the condition,body weight, sex and diet of the patient, the severity of any infection,time of administration and other clinical factors. Generally, the dailyregimen should be in the range of 1-1000 micrograms of polypeptide or 50to 5000 units (i.e., a unit being the concentration of polypeptide whichleads to half maximal stimulation in the T1165 assay) of polypeptide perkilogram of body weight.

The therapeutic method and compositions of the present invention mayalso include co-administration with other human factors. Exemplarycytokines or hematopoietins for such use include the known factors IL-1through IL-9, GM-CSF, G-CSF, M-CSF, MIF, Meg-CSF, the interferons, TNFand erythropoietin. Particularly desirable candidates for participationin IL-11 therapy may include IL-3 and IL-6. Growth factors like B cellgrowth factor, B cell differentiation factor, or eosinophildifferentiation factors may also prove useful in co-administration withIL-11. The dosage recited above would be adjusted to compensate for suchadditional components in the therapeutic composition. Progress of thetreated patient can be monitored by conventional methods.

Other uses for these novel polypeptides are in the development ofantibodies generated by standard methods for in vivo or in vitrodiagnostic or therapeutic use. Such antibodies may include bothmonoclonal and polyclonal antibodies, as well as chimeric antibodies or"recombinant" antibodies generated by known techniques. Also provided bythis invention are the cell lines generated by presenting IL-11 or afragment thereof as an antigen to a selected mammal, followed by fusingcells of the animal with certain cancer cells to create immortalizedcell lines by known techniques. The methods employed to generate suchcell lines and antibodies directed against all or portions of amammalian IL-11 polypeptide of the present invention are alsoencompassed by this invention.

The antibodies of the present invention may be utilized for in vivo andin vitro diagnostic purposes, such as by associating the antibodies withdetectable labels or label systems. Alternatively these antibodies maybe employed for in vivo and in vitro therapeutic purposes, such as byassociation with certain toxic or therapeutic compounds or moietiesknown to those of skill in this art.

The following examples illustratively describe the cloning, expressionand production of mammalian IL-11 and other methods and products of thepresent invention. These examples are for illustration and do not limitthe scope of the present invention.

EXAMPLE 1 Isolation of mRNA and Construction of cDNA Library

A primate cell line, pU34, was developed and was found to elaboratesignificant activity in the T1165 assay of Example 7 in the presence ofneutralizing antibody to IL-6. The PU-34 stromal cell line was derivedfrom a long term primate marrow culture by immortalization with adefective amphotropic transforming retroviral vector. The U19 retrovirusplasmid was constructed as previously reported P. S. Jat et al, J. ofVirol., 59:746-750 (1986)! and contains SV40 large T antigen sequenceand the neo-phosphotransferase sequence encoding G418-resistanceexpressed off the Moloney murine leukemia virus long terminal repeat. Anamphotropic producer clone was generated by infection of the packagingcell line ψAM R. Cone et al, Proc. Natl. Acad. Sci., USA, 81:6349-6353(1984)! with ecotropic viral harvest from ψ2U19-5 P. S. Jat, citedabove! followed by selection in 0.75 mg/ml G418.

One clone ψAMU19-BL produces recombinant SV40 virus at a titer of 5×10³G418-resistant CFU/ml when assayed on NIH/3T3 cells. Long term marrowcultures (LTMC) were established using standard methods and maintainedin Iscove's Modified Dulbecco's Medium (IMDM) supplemented with 10%fetal calf serum, 10% horse serum, 100 units/ml penicillin and 100 μg/mlstreptomycin (Sigma Chemical Co., St. Louis, Mo.) complete long termculture medium.

The LTMC adherent layer was infected 7 and 10 days after establishmentwith 2 ml of ψAMU19-BL viral stock in the presence of 8 μg/ml ofpolybrene (Aldrich Chemical Co., Inc., Milwaukee, Wis.) for 2.5 hours at33° C. Beginning three days after infection, the cultures were selectedin 0.5 mg/ml G418. Fourteen days after infection G418-resistant colonieswere picked and expanded in multiwell plates (Corning Glassware,Corning, N.Y.).

The conditioned medium from one cell line, designated PU-34, wasextensively analyzed based on its ability to support progenitor cells inlong term cultures. This cell line demonstrated the capacity to maintainmultipotent human and primate progenitor cells for up to three weeks inculture. In addition to known growth factor activities including IL-6,IL-7, GM-CSF, M-CSF, G-CSF and LIF/HILDA, the IL1-α-stimulated PU-34conditioned medium proved capable of stimulating the proliferation ofthe T1165.murine plasmacytoma cell line, which is normally responsive toIL-6 R. P. Nordan et al, cited above!, even in the presence of aneutralizing antiserum against human IL-6. This bioassay was used duringexpression cloning of a cDNA library generated from PU-34. The bioassayis described in detail in Example 7 below.

The cDNA library from PU-34 cells was prepared as follows: PU-34 cellswere stimulated for 24 hours with IL1-α at a concentration of 2units/mi. Poly adenylated RNA (poly A+ RNA) was prepared from thesecells by standard methods. Total RNA was extracted according to themethod of Chirgwin et al, Biochemistry, 18:5294-5299 (1979) from thestimulated pU34 cells. mRNA was prepared by oligo(dT)-cellulosechromatography H. Aviv et al, Proc. Natl. Acad. Sci. USA, 69:1408-1412(1972)!.

Five micrograms of mRNA was used to synthesize double-stranded cDNA asdescribed by Wong et al, cited above, with DNA polymerase I and RNAse Hin the second strand reaction T. Maniatis et al, cited above!. The Cos-1cell expression vector pXM Y. C. Yang et al, Cell 47:3-10 (1986)! waslinearized at the unique Xho I site and ligated to equimolar amounts ofsemi-Xho I adapted cDNA. The ligation reaction was used to transformcompetent E. coli (strain HB101) Y. C. Yang et al, cited above! togenerate a library of approximately 500,000 ampicillin-resistantcolonies.

EXAMPLE 2 DNA Preparation and COS-1 Cell Transfection

The expression cloning system previously described by G. G. Wong et al,cited above, was employed to isolate a cDNA encoding the IL-11 activityas follows.

Bacterial colonies were replicated onto nitrocellulose filters. Coloniesfrom each filter were scraped into L-broth and plasmid DNA was isolatedby previously described methods J. A. Meyers et al, J. Bacteriol.,127:1529-1536 (1976)!. Each primary DNA sample was prepared from a poolof 200-500 colonies.

Five micrograms of each plasmid DNA was used to transfect Cos-1 cells bythe diethylaminoethyl-dextran (DEAE) protocol with the addition of 0.1mM chloroquine L. M. Sompayrac et al, Proc. Natl. Acad. Sci. USA,78:7575-7578 (1981) and H. Luthman et al, Nucl. Acids Res., 11:1295-1308(1983)!; Y. C. Yang et al, cited above!. Culture supernatant fromtransfected Cos-1 cells was harvested 72 hours after transfection andassayed for T1165 stimulatory activity (see Example 7).

Of the 317 pools screened, plasmid DNA from the two positive pools whichcontained detectable levels of IL-6 (as determined by neutralizationwith anti-IL-6 antibody) and residual activity in the T1165 assay in thepresence of anti-IL-6 antibody, were re-transfected into COS-1 cells andtransfected supernatants were re-screened for activity in the T1165assay. One pool with such activity was selected and subdivided tocontain fewer number of clones. A pool from this group was selectedwhich demonstrated higher activity in the assay than the totalcollection of pools. Individual colonies were picked from this pool.Their DNAs were prepared, transfected, and the transfected supernatantswere examined for activity in the T1165 assay. Two positive clones wereidentified, one expressing IL-6 activity and the other expressingactivity unneutralized by anti-IL-6 antibodies. This latter pool wassubdivided and the transfection process repeated until a single positiveplasmid, called alternatively pC1R6 or pPU34-TRA, was obtained whichencoded the novel T1165 proliferation activity. This clone wasre-examined in the assay of Example 7.

The activity from the conditioned medium from pC1R6-transfected Cos-1cells was also compared with other cytokines, e.g., murine and humanIL-6 and murine GM-CSF. The conditioned medium stimulated measurableincorporation of ³ H-thymidine by T1165 cells, even at final dilutionsup to 1:1000. At optimal concentrations the novel cytokine supportedincorporation that was more than 100 fold above background levels.

The insert of this cDNA was sequenced by the dideoxy chain terminationmethod on super-coiled templates with synthetic oligonucleotide primersF. Sanger et al, Proc. Natl. Acad. Sci. USA, 74:5463-5467 (1977)!. Thenucleotide sequence of the pC1R6 cDNA shown in Table I contains a singlelong open reading frame of 597 nucleotides encoding a predicted 199amino acid polypeptide. Located immediately adjacent to the putativeinitiation codon is a stretch of 17-20 hydrophobic amino acids thatresembles a conventional protein secretory leader sequence.

Although the initial cDNA clone, pC1R6, proved to be incomplete,analysis of additional cDNAs revealed that this transcript containsapproximately 420 base pairs of 3' noncoding sequence with multiplecopies of the RNA instability sequence, ATTTA, believed to be animportant regulatory element for cytokine gene expression G. Shaw et al,Cell, 46:659-667 (1986)!.

EXAMPLE 3 Protein Analysis

The polypeptide encoded by the cDNA of pPU34-TRA was identified usingpulse-labeling experiments. Forty-eight hours after induction withchloroquine, culture supernatant from COS-1 cells transfected withrecombinant DNA of IL-11 clones was removed and cells were pulse-labeledwith 0.5 mCi ³⁵ S! methionine in 1.0 ml of DMEM for four hours at 37° C.Ten microliter samples of the radiolabelled supernatant were collectedand subjected to a 15% SDS-PAGE with the Laemmli buffer system on a 12%gel U. K. Laemmli, Nature, 227:680-685 (1970)!. After electrophoresis,the gel was immersed in a fluorography enhancing solution (Enhance; NewEngland Nuclear, Boston, Mass.), dried, and exposed to X-ray film.

SDS-polyacrylamide gel electrophoresis (SDS-PAGE) analysis ofconditioned medium from ³⁵ S-methionine labelled pC1R6-transfected cos-1cells revealed the presence of a prominent 20 kD species that was notpresent in mock-transfected controls consistent with the molecular massexpected for an approximately 180 amino acid secreted protein.

This size estimate as well as the lack of heterogeneity of the expressedprotein are in accordance with the absence of the consensus sequence(Asn-X-Thr/Ser) R. J. Winzler in "Hormonal Proteins and Peptides", ed.Li, C. H. (Academic Press, New York), pp. 1 (1973)! for the addition ofasparagine-linked carbohydrate. The predicted amino acid sequence of themature protein includes no cysteine residues, a feature not found withany other cytokine gene.

EXAMPLE 4 Human Cell Lines Expressing IL-11

Two human cell lines have been identified as sources of at least onespecies of IL-11. Specifically, the human lung fibroblast cell line,MRC-5, available from the American Type Culture Collection underAccession number ATCC CCL 171, when induced with one unit/ml ofrecombinant human IL-1-alpha (Genetics Institute, Inc.) and 10⁻⁷ Mphorbol 12-13 dibutyrate (Sigma), has been tested on the T1165 assay.The induced conditioned medium was observed to exhibit greater cpm onthe assay than does IL-6 at saturation levels, i.e., similar activity tothat exhibited by the induced conditioned medium of PU34. It has beennoted that the presence of IL-11 will enhance a low IL-6 signal. Inaddition, as detailed below, Northern blot of this cell line reveals thepresence of message for IL-11.

Additionally the human trophoblastic cell line, TPA30-1, available fromthe ATCC under Accession Number CRL 1583 also reveals uninduced thepresence of IL-11 message in Northern blots.

Other human sources for IL-11 may also be available and easilyidentified given the teachings of the present invention.

EXAMPLE 5 RNA Analysis

A. PU34

Five micrograms of total cellular RNA from bacterial IL-1-alpha inducedPU34 cells was electrophoresed through 1.2% agarose gel containing 2.2Mformaldehyde H. Lehrach et al, Biochemistry, 16:4743 (1977)!. Theformaldehyde-denatured RNA was transferred to nylon filter (Zetabind;Cuno, Meriden, Conn.) as described E. M. Southern, J. Mol. Biol.,98:503-517 (1975)! and probed with ³² P-labelled cDNA probes.

A cDNA probe was-made by cleaving cDNA inserts from the vector with XhoI restriction enzyme and labelled the inserts with ³² P-dCTP usingrandom oligonucleotides as primers in the presence of the large fragmentof DNA polymerase I A. P. Feinberg et al, Analy. Biochemistry, 132:6-13(1983)!. The nylon filter was prehybridized for 4 hours at 65° C.,hybridized with ³² P-dCTP labelled cDNA probe in hybridization solutionconsisted of 4XSSC, 0.5% SDS 5X Denhardt's solution and 100 ug/mldenatured salmon sperm DNA for 16 hours at 65° C. Other probes usedincluded human (rh) IL-1α, rhIL-2, rhIL-3, rhIL-4, rhIL-5, rhIL-6,rhIL-7, rhIL-9, rhGM-CSF, rhM-CSF, LIF/HILDA and primate IL-11.

After hybridization, the filter was washed two times with 2XSSC/0.1% SDSfor 30 minutes at 65° C., then with 0.2XSSC/0.1% SDS for 30 minutes at65° C. The filter was then dried and applied to X-ray film in thepresence of a calcium tungstate intensifying screen at -70° C.

This Northern blot analysis revealed that PU34 mRNA contained twospecies of IL-11 transcripts, with message sizes of approximately 2.5 kband approximately 1.5 kb which hybridize with the pCIR6 probe. The sizeof the cDNA sequence of Table I above correlates well with the smallermessage. This difference results from alternative splicing to yieldadditional 3' noncoding sequences in the larger transcript asdemonstrated by isolation and analysis of additional cDNA clones. Thepresence of the two transcripts by PU34 cells appears to be IL-1αregulated since neither transcript was evident in the absence of IL-1αinduction.

Neither transcript was identified by RNA blot analysis in preparationsof mRNA from the human T cell lines C10-MJ2 Leary et al, Blood, 69:953(1987)!, C5-MJ2 Arya et al, Science, 223:1086 (1984)!, and Mo Golde etal, Proc. Natl. Acad. Sci., USA, 77:593 (1980)! from lectin-stimulatedhuman peripheral blood lymphocytes or from human placental. Thus, itappears the only identified source of IL-11 is mesenchymal-derivedadherent cells.

B. MRC-5

The human fetal lung fibroblast cell line (MRC-5) as described by Jacobset al, Nature, 227:43 (1970) was found to express both transcriptsfollowing stimulation with 50 ng/ml phorbal myristate acetate (PMA) and1 unit/ml IL-1α.

As described above for PU34 RNA, two species of transcripts wereidentified with identical message sizes of approximately 2.5 kb andapproximately 1.5 kb in this cell line. Analysis of the human cDNAsequence isolated from the MRC-5 cell line revealed that the primate andhuman coding regions share approximately 95% identity at the nucleotidelevel.

C. TPA30-1

When the same procedures were performed on the human SV40-transformedtrophoblastic cell line, TPA30-1, using the same probe, only the largerapproximately 2.3 kb IL-11 message, was identified.

EXAMPLE 6 DNA Sequence Analysis

The nucleotide sequence of the cDNA clone of pPU34-TRA was determined asdescribed G. G. Wong et al and Y. C. Yang et al, cited above! bygenerating ordered sets of overlapping fragments via Bal 31 nucleasedigestion and subcloning into M13 vector M. Poncz et al, Proc. Natl.Acad. Sci. USA, 79:4298-4302 (1982); and J. Messing et al, Gene,19:269-276 (1982)!. Single-stranded DNA was prepared, and the nucleotidesequence was determined by the dideoxynucleotide chain-terminationprocedure F. Sanger et al, Proc. Natl. Acad. Sci. USA, 74:5463-5467(1977)!. This nucleotide sequence appears in Table I above.

EXAMPLE 7 Biological Activity in Assays

A. T1165 Proliferation Assay

T1165 IL-6 dependent murine plasmacytoma cells R. P. Nordan et al,Science, 233:566 (1986); and obtained from Dr. Nordan, NationalInstitutes of Health! are routinely grown in RPMI supplemented with 10%heat-inactivated fetal calf serum, 2 mM glutamine, 100 u/ml penicillin,100 μg/ml streptomycin (all Gibco, Grand Island, N.Y.), 5×10⁻⁵ M betamercaptoethanol (Sigma Chemical Co., St. Louis, Mo.), and supplementedwith 10-20 U/ml recombinant human IL-6 produced in CHO cells (GeneticsInstitute, Inc.). Two to four days following passage, the cells areremoved from culture, washed to remove residual IL-6 and resuspended ata concentration of 7.5×104 to 1×10⁵ cells/mi.

Serial dilutions of the sample to be assayed (either PU34 conditionedmedium or pC1R6-transfected Cos cell conditioned medium) are made induplicate in 100 E1 of culture medium without IL-6 on 96-well microtiterplates. 100 μl of the above cell suspension is then added to each welland the plates are incubated at 37° C. for 2-3 days; 0.5 μCi of ³H-thymidine DuPont, Wilmington, Del.! is added per well for the finalsix hours of the assay. Cells are harvested onto GFC type C filter paper(LKB), washed with water and ethanol and dried. The filters are thenimmersed in scintillation fluid and counted on an LKB flatbedscintillation counter. Proliferation is measured by ³ H-thymidineuptake.

Induced conditioned medium from the PU34 cells caused greaterproliferation of the T1165 cells than saturating levels of IL-6,suggesting the presence of another factor. When assayed in the presenceof antibody to human IL-6, a low but significant activity remained inthe conditioned medium. Fractionated samples of conditioned medium fromIL-1-induced PU34 containing very low levels of IL-6 were also assayedwith and without antibody to human IL-6 and the results suggested thepresence of a factor that was proliferative to a low degree by itselfand capable of synergizing with low levels of IL-6.

COS cell supernatants from transfection of the pU34 library were alsoassayed for activity, alone and in the presence of a cocktail ofantibody to human IL-6 plus suboptimal levels of murine IL-6. Theantibody is capable of neutralizing primate IL-6 produced by the PU34cells, but not able to neutralize murine IL-6. Therefore, a synergizingfactor could be screened for without interference from the PU34 IL-6present in the library.

The mature IL-11 protein of Table I is characterized by a half-maximalactivity of 100 dilution units per ml in this assay.

B. B Cell Plaque Forming Assay

A B Cell plaque forming assay was performed on COS cell expressing Il-11according to the procedures described in R. M. O'Hara et al, J.Immunol., 141:2935-2942 (1988). The murine plaque forming assay wasperformed by incubating 7.5×10⁶ spleen cells from naive C57B1/6 micewith 3×10⁶ 4-hydroxy-3-nitrophenyl-acetyl-modified horse red blood cells(NP-HRBC) in 0.75 ml Mishell-Dutton media R. I. Mishell et al, J. Exp.Med. 126:423-442 (1967)! supplemented with 5% fetal calf serum with orwithout test samples (COS cell conditioned media containing IL-11) for 5days. NP-coupled horse red blood cells (H-RBC) or sheep red blood cells(S-RBC) were prepared by reaction of 10 mg NP-O-Succinimide (CambridgeBiochemical, Inc., Cambridge, England) in dimethyl formamide (SigmaChemical Co., St. Louis, Mo.) with 1 ml packed H-RBC or S-RBC (ColoradoSerum Co., Denver, CO) as has been described previously P. B. Hausman etal, J. of Immunol., 134:1388-1396 (1985)!.

These cultures were fed daily by addition of 0.1 ml supplemental mediumcontaining 5% fetal calf serum without test samples (the conditionedmedia). NP-responsive B-cells were identified at the end of the cultureperiod using the NP-coupled-sheep RBC plaque assay as described byDresser et al in "Handbook in Experimental Immunology" (D. M. Weir,Blackwell, Oxford), p. 271 (1973) with the percent response calculatedby comparing the numbers of plaques obtained from cultures supportedwith the conditioned medium containing IL-11 with those culturessupplemented with medium alone. In a typical experiment, backgroundresponses in the absence of exogenous factors yielded 6000 NP-specificplaque forming cells per 7.5×10⁶ cells plated.

The results of such as assay can be seen in FIG. 1. The percent ofcontrol response is the increase in the development of NP-responsive Bcells in 5 day cultures of naive spleen cells stimulated with NP-HRBCsupported by the indicated dilution of pC1R6-transfected cos-1 cellconditioned medium compared to control cultures supplemented with mediumalone. COS-produced mammalian IL-11 produces a 2 and one-half to 3-foldincrease in plaque forming units/culture in this assay, indicating theIL-11 plays either a direct role in B cell stimulation anddifferentiation, or an indirect role in stimulating T cells to secreteother cytokines which influence the B cell response.

C. Murine Fibrin Clot Assay

COS cell produced mammalian IL-11 was also examined for activity in themegakaryocyte colony formation assay performed substantially asdescribed in S. Kuriya et al, Exp. Hematol., 15:896-901 (1987) andmodified by the addition of 2% calf serum. Briefly described, the murinecolony forming unit megakaryocyte (CFU-Meg) assay was performed byplating 2.5×10⁵ murine bone marrow cells in 0.4 ml of IMDM supplementedwith 20% fetal calf serum in 6 well dishes. Clot formation was initiatedby addition of 0.25 mg fibrinogen and 0.25 units thrombin (SigmaChemical Co., St. Louis, Mo.) at 37° C. Test samples at variousdilutions were added to the fibrin clot and cultures subsequentlyincubated for 6 days at 37° C. The clots were fixed with 2.5%glutaraldehyde and stained with 0.5 mg/ml acetylthiocholine iodide asdescribed in S. Kuriya et al, cited above and A. Nakeff et al, Proc.Soc. Ext. Biol. Med., 151:587-590 (1976). Positive colonies (containingonly megakaryocytes) were enumerated under direct microscopy. Colonynumbers were evaluated in duplicate.

FIG. 2 illustrates the results. The colony number represents the totalnumber of megakaryocyte colonies (acetylcholinesterase positive cells)in 6 day cultures of mouse bone marrow cells supported by: (1) a 1:10dilution of canine aplastic anemia serum; (2) 150 units/ml murine IL-3;(3) no stimulus; and dilutions of (4) 1:10 or (5) 1:50pC1R6-transfected-cos-1 cell conditioned medium alone or dilutions of(6) 1:10 or (7) 1:50 of pC1R6-transfected-cos-1 cell conditioned mediumsupplemented with 150 units/ml murine IL-3.

When IL-11 was tested in this assay alone, little response was detected.However, when IL-11 was tested in this assay in the presence ofrecombinant murine IL-3, the assay results demonstrated that thecombination of IL-11 and IL-3 stimulated the production and maturationof megakaryocyte cells in this assay to a significant degree. This assaydemonstrated that mammalian IL-11 has a synergistic effect with IL-3 inthe stimulation of megakaryocyte development.

EXAMPLE 8 Obtaining Human IL-11

To obtain the cloned sequence for human IL-11, the PU34 IL-11 cDNA whichhybridized to the human IL-11 mRNA in Example 5 above, was employed toscreen a cDNA library prepared from the human lung fibroblast cell line,MRC-5, described above. Recombinants from this library were plated andduplicate nitrocellulose replicase made of the plates. These replicasewere hybridized overnight at 65° C. in standard hybridization solution(4XSSC) with the mammalian IL-11 cDNA labelled with ³² P-dCTP using therandom priming labelling technique A. P. Feinberg, cited above!. Thefilters were then washed in 0.2XSSC at the same temperature until thebackground radioactivity was lowered to an acceptable level to permitdetection of specifically hybridizing sequences. Colonies found tohybridize to the mammalian IL-11 probe on the duplicate filters werepicked and used to prepare plasmid DNA.

The full sequence for human IL-11 was determined according to methodsanalogous to those described above for the isolation of mammalian IL-11from the PU34 cell line. The human sequence is shown also in Table I.Where the human sequence nucleotides differed from the primate sequence,the human nucleotide is provided above the primate nucleotide sequencein Table I.

Alternatively, oligonucleotides may be constructed from the sequence ofTable I with appropriate restriction sites for subcloning purposes, andthe Polymerase Chain Reaction employed to generate the human DNAsequence for IL-11. For example, the following oligonucleotides aresynthesized:

    5' oligonucleotide: 5' ATGGATCCACATGAACTGTGTTTGCCG 3'

    3' oligonucleotide: 5' TCAAGCTTTCACAGCCGAGTCTTCAGC 3'

These oligonucleotides are then employed in the Polymerase ChainReaction in the cDNA library of MRC-5 or TPA30-1, to obtain the DNAsequence for human IL-11 therefrom. The PCR technique is performedaccording to procedures now standard in the art. The PCR productobtained is then subcloned into an appropriately-digested pXM, or other,expression vector. For the above oligonucleotides, the pXM vector wouldbe digested with BamHI and HindIII for the subcloning.

Still a third method to obtain the sequence of human IL-11 involvesscreening a human genomic library using the sequence of Table I as aprobe.

EXAMPLE 9 Expression of Recombinant IL-11

To produce recombinant mammalian IL-11 including the human factor, thecDNA encoding it is transferred into an appropriate expression vector ofwhich numerous types are known in the art for mammalian, insect, yeast,fungal and bacterial expression by standard molecular biologytechniques. See, e.g., Y. C. Yang et al., Cell, 47:3-10 (1986).

As described previously for mammalian IL-11, the cDNA for human IL-11 issynthesized using standard techniques and cloned into the expressionvector, pXM (Yang et al., cited above). This vector permits theexpression of cDNA inserts in mammalian cells, e.g., COS-1 cells. pXMcontains the SV40 enhancer, major adenovirus late promoter, tripartiteleader sequence, and small hybrid intervening sequence, the DHFR codingsequence, SV40 late message poly A addition site and adenovirus VaIgene. This vector may be linearized with the endonuclease enzyme XhoIand ligated to equimolar amounts of IL-11 cDNA which has been previouslymodified by the addition of synthetic oligonucleotides that generatecomplementary XhoI cohesive ends. Such oligonucleotides are commerciallyavailable Collaborative Research, Lexington, Mass.!.

Another vector which has been shown to express cytokines well in CHOcells is pEMC2B1. This vector may be derived from pMT2pc which has beendeposited with the American Type Culture Collection (ATCC), Rockville,Md. (USA) under Accession Number ATCC 40348. The DNA is linearized bydigestion of the plasmid with PstI. The DNA is then blunted using T₄ DNApolymerase. An oligonucleotide 5' TGCAGGCGAGCCTGAATTCCTCGA 3' is thenligated into the DNA, recreating the PstI site at the 5' end and addingan EcoRI site and XhoI site before the ATG of the DHFR cDNA. Thisplasmid is called pMT21. pMT21 is cut with EcoRI- and XhoI which cleavesthe plasmid at two adjacent cloning sites. An EMCV fragment of 508 basepairs was cut from pMT₂ ECAT₁ S. K. Jong et al., J. Virol., 63:1651-1660(1989)! with the restriction enzymes EcoRI and TaqαI. A pair ofoligonucleotides 68 nucleotides in length were synthesized to duplicatethe EMCV sequence up to the ATG. The ATG was changed to an ATT, and a Cis added, creating a XhoI site at the 3' end. A TaqαI site is situatedat the 5' end. The sequences of the oligonucleotides were: 5'CGAGGTTAAAAAACGTCTAGGCCCCCCGAACCACGGGGACGTGGTTTTCCTTT GAAAAACACGATTGC 3'and its complementary strand.

Ligation of the pMT21 EcoRI-to-XhoI fragment to the EMCV EcoRI-to-TaqαIfragment and to the TaqαI/XhoI oligonucleotides produced the vectorpEMC2B1. This vector contains the SV40 origin of replication andenhancer, the adenovirus major late promoter, a cDNA copy of themajority of the adenovirus tripartite leader sequence, a small hybridintervening sequence, an SV40 polyadenylation signal and the adenovirusVA I gene, DHFR and β-lactamase markers and an EMC sequence, inappropriate relationships to direct the high level expression of thedesired cDNA in mammalian cells. The EMC2B1 vector is linearized withthe endonuclease enzyme EcoRI and subsequently ligated in equimolaramount separately to the cDNA encoding IL-11 that was previouslymodified by addition of synthetic oligonucleotides that generate EcoRIcomplementary ends to generate constructs for expression.

The desired vector containing IL-11 is then introduced into appropriatehost cells by conventional genetic engineering techniques. Thetransformed cells are cultured and the expressed IL-11 is recovered andpurified from the culture medium using standard techniques.

A. Mammalian Cell Expression

To obtain expression of the IL-11 polypeptide in mammalian host cells,the pXM vector containing the IL-11 DNA sequence is transfected onto COScells as described in Example 2. The conditioned medium from thetransfected COS cells contains IL-11 biological activity as measured inthe T1165 assay. Similarly the pEMC-2B1 construct containing the cDNAfor IL-11 is transfected into CHO cells.

One skilled in the art can also construct other mammalian expressionvectors comparable to the pXM/IL-11 vector by, e.g., inserting the DNAsequence of IL-11 from the respective plasmids with XhoI and employingwell-known recombinant genetic engineering techniques and other knownvectors, such as pJL3 and pJL4 Gough et al., EMBO J., 4:645-653 (1985)!and pMT2 (starting with pMT2-VWF, ATCC #67122; see PCT applicationPCT/US87/00033).

The transformation of these vectors into appropriate host cells canresult in expression of the IL-11 polypeptides. Mammalian host cellsother than COS cells may also be employed in IL-11 expression. Forexample, preferably for stable integration of the vector DNA, and forsubsequent amplification of the integrated vector DNA, both byconventional methods, CHO cells may be employed as a mammalian host cellof choice.

Once the vectors and host cells are selected and transformed, stabletransformants are screened for expression of the IL-11 by standardimmunological or enzymatic assays. The presence of the DNA or mRNAencoding the IL-11 polypeptides may be detected by standard proceduressuch as Southern or Northern blotting. Transient expression of the DNAencoding the polypeptides during the several days after introduction ofthe expression vector DNA into suitable host cells is measured withoutselection by activity or immunologic assay, e.g., the T1165 assay, ofthe proteins in the culture medium.

B. Bacterial Expression Systems

Similarly, one skilled in the art could manipulate the sequence of IL-11by eliminating any mammalian regulatory sequences flanking the codingsequences and inserting bacterial sequences to create bacterial vectorsfor intracellular or extracellular expression of the IL-11 polypeptidesof the invention by bacterial cells.

The DNA encoding the factor may be further modified to contain differentcodons for bacterial expression as is known in the art. Preferably themature IL-11 sequence (the nucleotide encoding amino acids 21 to 199 inTable I) is operatively linked inframe to a nucleotide sequence encodinga secretory leader polypeptide permitting bacterial expression,secretion and processing of the mature variant protein, also as is knownin the art. The compounds expressed in bacterial host cells may then berecovered, purified, and/or characterized with respect tophysiochemical, biochemical and/or clinical parameters, all by knownmethods.

Alternatively, the IL-11 may be expressed as a cytoplasmic protein in E.coli. In this case, the molecule would most likely have to be refoldedafter complete denaturation with guanidine hydrochloride, a process alsoknown in the art. The presently preferred method for expression of IL-11in E. coli, involves removing the first 31 codons of the human IL-11sequence. The following sequence is then attached at codon 32 of themature human IL-11 sequence: ##STR18##

C. Insect or Yeast Cell Expression

Similar manipulations can be performed for the construction of an insectvector See, e.g., procedures described in published European patentapplication 155,476! for expression in insect cells. A yeast vectorcould also be constructed employing yeast regulatory sequences forintracellular or extracellular expression of the proteins of the presentinvention by yeast cells. See, e.g., procedures described in publishedPCT application WO 86/00639 and European patent application EP 123,289.!

EXAMPLE 10 Construction of CHO Cell Lines Expressing High Levels ofIL-11

One method for producing high levels of the IL-11 polypeptides of theinvention from mammalian cells involves the construction of cellscontaining multiple copies of the heterologous IL-11 gene. Theheterologous gene can be linked to an amplifiable marker, e.g., thedihydrofolate reductase (DHFR) gene for which cells containing increasedgene copies can be selected for propagation in increasing concentrationsof methotrexate (MTX) according to the procedures of Kaufman & Sharp, J.Mol. Biol., (1982) supra. This approach can be employed with a number ofdifferent cell types. Alternatively, the IL-11 cDNA and drug resistanceselection gene (e.g., DHFR) may be introduced into the same vector. Apreferred vector for this approach is pEMC2B1.

For example, the pXM vector containing a IL-11 gene in operativeassociation with other plasmid sequences enabling expression thereof andthe DHFR expression plasmid pAdA26SV(A) 3 (Kaufman & Sharp, Mol. CellBiol., 3(9):1598-1608 (1983) can be co-introduced into DHFR-deficientCHO cells, DUKX-BII, by calcium phosphate coprecipitation andtransfection.

Alternatively, the pEMC-2B1 vector containing the IL-11 gene inoperative association with other plasmid sequences enabling expressionthereof is introduced into DHFR-deficient CHO cells, DUKX-BII, byprotoplast fusion and transfection. The IL-11 gene and DHFR marker geneare both efficiently expressed when IL-11 is introduced into pEMC2B1.The IL-11 gene may be introduced into pMT2 as previously mentioned andthe resultant vector used in place of pXM/IL-11 and pAdA26SV(A)3.

DHFR expressing transformants are selected for growth in alpha mediawith dialyzed fetal calf serum. Transformants are checked for expressionof IL-11 by bioassay, immunoassay or RNA blotting and positive pools aresubsequently selected for amplification by growth in increasingconcentrations of MTX (sequential steps in 0.02, 0.2, 1.0 and 5 uM MTX)as described in Kaufman et al, Mol. Cell Biol., 5:1750 (1983). Theamplified lines are cloned, and biologically active IL-11 polypeptideexpression is monitored by the T1165 assay. IL-11 polypeptide expressionis expected to increase with increasing levels of MTX resistance.

In any of the expression systems described above, the resulting celllines can be further amplified by appropriate drug selection, resultingcell lines recloned and the level of expression assessed using the T1165assay described herein.

The IL-11 expressing CHO cell lines can be adapted to growth inserum-free medium. Homogeneous IL-11 can be isolated from conditionedmedium from the cell line using methods familiar in the art, includingtechniques such as lectin-affinity chromatography, reverse phase HPLC,FPLC and the like.

EXAMPLE 11 Effect of IL-11 on Proliferation in Culture of Early MurineProgenitors

Methylcellulose cell cultures were established in 35 mm Lux suspensionculture dishes (#5221R, Nunc, Inc. Naperville, Ill.).

5-Fluorouracil (5-FU) (Adria Laboratories, Columbia, Ohio) wasadministered intravenously through the tail veins of 10 to 15 week oldfemale BDF₁ mice ARS Sprague Dawley, Indianapolis, Ind.! at 150 mg/kgbody weight T. Suda et al, J. Cell. Physiol., 117:308-318 (1983) and G.S. Hodgson et al, Nature, 281:381-382 (1979)!. Single cell suspensionswere prepared from pooled femurs or spleens of three mice. Light density(<1,077) mononuclear cells were collected from the interface ofFicoll-Paque after centrifugation at 400 g. After overnight adherence ofthese cells to plastic dishes, nonadherent mononuclear (bone marrow andspleen) cells were harvested 2 and 5 days after 5-FU injection,respectively.

One ml of culture contained 2×10⁴ marrow cells from normal mice, 5×10⁴marrow cells or 1×10⁶ spleen cells from 5-FU-treated mice, α-medium(Flow Laboratories, Inc., McLean, Va.), 1.2% 1,500 cps methylcellulose(Fisher Scientific Co., Norcross, Ga.), 30% fetal calf serum (FCS)(Hyclone Laboratories, Inc., Logan, Utah), 1% deionized fraction Vbovine serum albumin (BSA) (Sigma Chemical Co., St. Louis, Mo.), 1×10⁻⁴M 2-mercaptoethanol (Eastman Organic Chemicals, Rochester, N.Y.) andhemopoietic factors. Dishes were incubated at 37° C. in a humidifiedatmosphere flushed with 5% CO₂. Except for megakaryocyte colonies,colonies consisting of 50 or more cells were scored on an invertedmicroscope on the specified day of incubation. Megakaryocyte colonieswere scored when they contained four or more megakaryocytes.Abbreviations for colony types are as follows: GM,granulocyte/macrophage; Mast, mast cell colonies; E, erythroid bursts;M, megakaryocyte colonies; GMM, granulocyte/macrophage/megakaryocytecolonies T. Nakahata et al, J. Cell. Physiol., 111:239-246 (1982)!;GEMM, granulocyte/erythrocyte/macrophage/megakaryocyte colonies T.Nakahata et al, cited above; and A. A. Fauser et al, Blood, 52:1243-1248(1978)!; and B1, blast cell colonies T. Nakahata et al, Proc. Natl.Acad. Sci. USA, 79:3843-3847 (1982); and T. Suda et al, cited above!.

The hemopoietic potential of the blast cell colonies was determined byblast cell colony replating. Between days 5 and 15 of incubation,individual blast cell colonies containing 50 to 150 cells were pickedwith an Eppendorf pipet and replated in secondary methylcellulosecultures containing 2 U/ml human urinary erythropoietin (Ep) activity of370 U per mg, available from Dr. Makoto Kawakita, Kumamoto UniversityMedical School, Kumamoto, Japan!, 1% (v/v) concentrated (X20)supernatant of cultures of WEHI-3 cells.

Blast cells were also used as pure target populations of hemopoieticcells to determine whether the observed effects of IL-11 were direct ordue to the release of other factors. One million day-4 post-5-FU spleencells were cultured in the presence of 100 U/ml of recombinant murineIL-3. IL-3 was conditioned by Chinese Hamster Ovary (CHO) cells that hadbeen genetically engineered to produce murine IL-3 to high titer(approximately 30,000 U/ml). On day 8 of culture, individual blast cellcolonies (between 50 to 150 cells) were picked from cultures, pooled,washed twice with medium and replated in secondary cultures eachcontaining different combinations of factors.

Recombinant human IL-6 with specific activity of 4×10⁶ U/mg protein wasexpressed in E. coli. IL-11 was medium conditioned (CM) by COS-1 cellstransfected with cDNA encoding the murine plasmacytoma-stimulatoryactivity S. R. Paul et al, Proc. Natl. Acad. Sci. USA, in press (1990)!.

A. Colony Formation from Marrow Cells of Normal Mice

Colony formation from normal marrow cells was supported by IL-11. In thepresence or absence of 2 U/ml Ep, IL-11 gave rise to colonies in adose-dependent manner. A 1:100 dilution of IL-11 supported maximalcolony formation. However, the total number of colonies detected on day8 or day 16 of incubation with IL-11 was significantly fewer than incultures with IL-3. The colonies found in IL-11-containing cultures werepredominantly of the GM type, although some multilineage (GMM and GEMM)colonies were also observed. IL-11 in a 1:100 dilution supportedformation of three blast cell colonies on day 16 of incubation.

B. Colony Formation from Marrow Cells of 5-FU-Treated Mice

Colony formation from marrow cells harvested two days after injection of150 mg/kg 5-FU T. Suda et al., cited above; and G. S. Hodgson et al.,cited above! in cultures established in the presence of IL-11, IL-6,IL-3 singly and in various combinations was studied to determine whetherIL-11 acts synergistically with IL-3 in supporting the proliferation ofprimitive progenitors.

Addition of IL-11 at final dilutions of 1:100 and 1:1,000 to an optimalconcentration of IL-3 significantly enhanced colony formation. Inparticular, in the presence of a 1:100 dilution of IL-11 and IL-3 thekinetics of colony formation was accelerated as compared to thatsupported by the individual factors. The time course of colony formationas well as the total number of colonies supported were similar to thoseobserved with the combination of IL-6 and IL-3. IL-11 alone in a 1:100dilution supported scant colony formation after a long period ofincubation. These results indicated that IL-11 enhances IL-3-dependentproliferation of primitive progenitors.

The effects of a combination of IL-11 and IL-6 on the kinetics of colonyformation from day-2 post-5-FU marrow cells relative to the effects ofindividual synergistic factors were tested separately. IL-6 and IL-11significantly accelerated IL-3-dependent colony formation. The effectsof the combination of IL-6 and IL-11, however, did not differ from thoseof individual factors.

C. Serial Observations of Blast Cell Colony Development from Day-4Post-5-FU Spleen Cells

The growth rates of individual blast cell colonies were serially plottedthrough culture mapping studies. The results indicated that thesynergistic effect of IL-11 results from a decrease in the time stemcells spend in the dormant state, an effect very similar to thatobserved with IL-6 or G-CSF because the growth rates were notstatistically different in these culture systems.

D. Comparison of the Replating Potentials of Blast Cell Colonies

The proliferative potentials of blast cell colonies that respond toIL-11 and IL-6 were tested by replating experiments. Significantvariations in the secondary replating efficiencies were seen amongindividual blast cell colonies as reported previously K. Ikebuchi etal., Blood, 72:2007-2014 (1988)!. There was, however, no significantdifferences in the replating efficiencies of blast cell colonies grownin the three different primary culture conditions.

Similar to previous observations K. Ikebuchi et al., cited above!, thepercentages of secondary GEMM colonies in secondary colonies and theincidences of secondary GEMM colonies per blast cell colonies weresignificantly higher from the primary blast cell colonies identified incultures containing IL-11 or IL-6 than those seen in cultures containingIL-3 alone. There were no significant differences in these parametersbetween cultures containing IL-11 plus IL-3 and cultures containing IL-6plus IL-3.

These results indicated that the synergistic activities of IL-11 andIL-6 are similar and that the increases in the incidences of secondaryGEMM colonies may be due to shortening of the G. period of stem cellsduring blast cell colony formation K. Ikebuchi et al., cited above!.

E. Replacing Studies of Pooled Blast Cells

Target cells obtained by pooling blast cells from early stages ofcultures supported by IL-3 were used to compare the direct effects ofIL-11 and IL-6 on GM colony formation, Pooled blast cells are devoid ofstromal cells and express very high replating efficiencies.

Blast cell colonies containing 50 to 150 cells identified in culturescontaining IL-3 were picked and pooled, and were replated in secondarycultures containing IL-11, IL-6 or IL-3 in the presence of 2 U/ml Ep.These date indicate that at least 70% of the blast cells are hemopoieticprogenitors.

While the combination of IL-3 and Ep supported formation of a variety ofsingle lineage and multilineage colonies, IL-11 and Ep supported theformation of only macrophage colonies. The combination of IL-6 and Epsupported formation of a similar number of pure macrophage colonies butalso neutrophil/macrophage colonies. The macrophage colonies supportedby IL-11 were smaller than the macrophage colonies supported by IL-6.

These results indicated that IL-11 and IL-6 interact with overlappingbut different progenitor subsets and that IL-11 preferentially supportsthe macrophage progenitor population.

F. The Effects of. Neutralizing Anti-IL-6 Antibody on the SynergisticEffects of IL-11

In order to confirm that the direct colony-supporting ability betweenIL-11 and IL-6 was not a result of the crude nature of the Cos cell CM,neutralizing anti-IL-6 antibody, which is known to inhibit Cos-derivedIL-6, was used to study the synergistic effects of IL-11 and IL-6 onIL3-dependent proliferation from dormant progenitors.

In the presence of IL-6 or IL-11 and in the absence of antibodies,colony development from day-4 post-5-FU spleen cells was significantlyhastened as indicated by the number of colonies on day 8. When anti-IL-6antibody was present, the synergistic effects of IL-6 were completelyabrogated while the effects of IL-11 were not. The effects of theantibody persisted until day 16. These results excluded the possibilitythat the apparent synergistic effects in Cos cell CM were mediated byIL-6.

The conditioned medium (CM) of COS cells transfected with IL-11 cDNA hasbeen found to augment IL-3-dependent proliferation of multipotentialprogenitors in culture, an activity originally associated with IL-6. Themechanism of the augmentation appears to be shortening of the G. periodof dormant stem cells.

The foregoing descriptions detail presently preferred embodiments of theinvention. Numerous modifications and variations in practice of thisinvention are expected to occur to those skilled in the art. Suchmodifications and variations are encompassed within the followingclaims.

    __________________________________________________________________________    SEQUENCE LISTING                                                              (1) GENERAL INFORMATION:                                                      (iii) NUMBER OF SEQUENCES: 4                                                  (2) INFORMATION FOR SEQ ID NO:1:                                              (i) SEQUENCE CHARACTERISTICS:                                                 (A) LENGTH: 1100 base pairs                                                   (B) TYPE: nucleic acid                                                        (C) STRANDEDNESS: double                                                      (D) TOPOLOGY: linear                                                          (ii) MOLECULE TYPE: cDNA                                                      (iii) HYPOTHETICAL: NO                                                        (iv) ANTI-SENSE: NO                                                           (ix) FEATURE:                                                                 (A) NAME/KEY: CDS                                                             (B) LOCATION: 73..669                                                         (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                                       GGGAAGGTGGAAGGGTTAAAGGCCCCCGGCTCCCTGCCCCCTGCCCTGGGGAACCCCTGG60                CCCTGCGGGGACATGAACTGTGTTTGCCGCCTGGTCCTGGTCGTGCTG108                           MetAsnCysValCysArgLeuValLeuValValLeu                                          1510                                                                          AGCCTGTGGCCAGATACAGCTGTTGCCCCTGGGCCACCACCTGGCTCC156                           SerLeuTrpProAspThrAlaValAlaProGlyProProProGlySer                              152025                                                                        CCTCGAGCTTCCCCAGACCCTCGGGCCGAGCTGGACAGCACCGTGCTC204                           ProArgAlaSerProAspProArgAlaGluLeuAspSerThrValLeu                              303540                                                                        CTGACCCGCTCTCTCCTGGAGGACACGCGGCAGCTGACTATACAGCTG252                           LeuThrArgSerLeuLeuGluAspThrArgGlnLeuThrIleGlnLeu                              45505560                                                                      AAGGACAAATTCCCAGCTGACGGGGACCACAACCTGGATTCCCTGCCC300                           LysAspLysPheProAlaAspGlyAspHisAsnLeuAspSerLeuPro                              657075                                                                        ACCCTGGCCATGAGCGCGGGGGCACTGGGAGCTCTACAGCTCCCGAGT348                           ThrLeuAlaMetSerAlaGlyAlaLeuGlyAlaLeuGlnLeuProSer                              808590                                                                        GTGCTGACAAGGCTGCGAGCGGACCTACTGTCCTACCTGCGGCATGTG396                           ValLeuThrArgLeuArgAlaAspLeuLeuSerTyrLeuArgHisVal                              95100105                                                                      CAGTGGCTGCGTCGGGCAATGGGCTCTTCCCTGAAGACCCTGGAGCCT444                           GlnTrpLeuArgArgAlaMetGlySerSerLeuLysThrLeuGluPro                              110115120                                                                     GAGCTGGGCACCCTGCAGACCCGGCTGGACCGGCTGCTGCGCCGGCTG492                           GluLeuGlyThrLeuGlnThrArgLeuAspArgLeuLeuArgArgLeu                              125130135140                                                                  CAGCTCCTGATGTCCCGCCTGGCCCTGCCCCAGCTGCCCCCAGACCCG540                           GlnLeuLeuMetSerArgLeuAlaLeuProGlnLeuProProAspPro                              145150155                                                                     CCGGCGCCCCCGCTGGCGCCCCCCTCCTCAACCTGGGGGGGCATCAGG588                           ProAlaProProLeuAlaProProSerSerThrTrpGlyGlyIleArg                              160165170                                                                     GCCGCCCACGCCATCCTGGGGGGGCTGCACCTGACACTTGACTGGGCC636                           AlaAlaHisAlaIleLeuGlyGlyLeuHisLeuThrLeuAspTrpAla                              175180185                                                                     GTGAGGGGGCTACTGCTGCTGAAGACTCGGCTGTGACCCGAGGCCCAGAGCCA689                      ValArgGlyLeuLeuLeuLeuLysThrArgLeu                                             190195                                                                        CCACCGTCCTTCCAAAGCCACATCTTATTTATTTATTTATTTCGGTACTGGGGGCGAAAC749               AGCCAGGTGATCCCCCTGCCTTTAGCTCCCCCTAGTTAGAGACAGTCCTTCCGTGAGGCT809               GGGGGGCATCTGTGCCTTATTTATACTTATTTATTTCAGGAGCGGGGGTGGGCTCCTGGG869               TCCCCGAGGAGGAGGGAGCTGGGGTCCCGGATTCTTGTGTCCACAGACTTCTGCCCTGGC929               TCCTCCCCCTCGAGGCCTGGGCAGGAATACATACTATTTATTTAAGCAATTACTTTTCAT989               GTTGGGGTGGGGAGGGAGGGGAAAGGGAAGCCTGGGTTTTTGTACAAAAATGTGAGAAAC1049              CTTTGTGAGACGGAGAACAAGGAATTAAATGTGTCATACATAAAAAAAAAA1100                       (2) INFORMATION FOR SEQ ID NO:2:                                              (i) SEQUENCE CHARACTERISTICS:                                                 (A) LENGTH: 199 amino acids                                                   (B) TYPE: amino acid                                                          (D) TOPOLOGY: linear                                                          (ii) MOLECULE TYPE: protein                                                   (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                                       MetAsnCysValCysArgLeuValLeuValValLeuSerLeuTrpPro                              151015                                                                        AspThrAlaValAlaProGlyProProProGlySerProArgAlaSer                              202530                                                                        ProAspProArgAlaGluLeuAspSerThrValLeuLeuThrArgSer                              354045                                                                        LeuLeuGluAspThrArgGlnLeuThrIleGlnLeuLysAspLysPhe                              505560                                                                        ProAlaAspGlyAspHisAsnLeuAspSerLeuProThrLeuAlaMet                              65707580                                                                      SerAlaGlyAlaLeuGlyAlaLeuGlnLeuProSerValLeuThrArg                              859095                                                                        LeuArgAlaAspLeuLeuSerTyrLeuArgHisValGlnTrpLeuArg                              100105110                                                                     ArgAlaMetGlySerSerLeuLysThrLeuGluProGluLeuGlyThr                              115120125                                                                     LeuGlnThrArgLeuAspArgLeuLeuArgArgLeuGlnLeuLeuMet                              130135140                                                                     SerArgLeuAlaLeuProGlnLeuProProAspProProAlaProPro                              145150155160                                                                  LeuAlaProProSerSerThrTrpGlyGlyIleArgAlaAlaHisAla                              165170175                                                                     IleLeuGlyGlyLeuHisLeuThrLeuAspTrpAlaValArgGlyLeu                              180185190                                                                     LeuLeuLeuLysThrArgLeu                                                         195                                                                           (2) INFORMATION FOR SEQ ID NO:3:                                              (i) SEQUENCE CHARACTERISTICS:                                                 (A) LENGTH: 1208 base pairs                                                   (B) TYPE: nucleic acid                                                        (C) STRANDEDNESS: double                                                      (D) TOPOLOGY: linear                                                          (ii) MOLECULE TYPE: cDNA                                                      (iii) HYPOTHETICAL: NO                                                        (iv) ANTI-SENSE: NO                                                           (ix) FEATURE:                                                                 (A) NAME/KEY: CDS                                                             (B) LOCATION: 138..734                                                        (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:                                       GGCTCAGGGCACATGCCTCCCCTCCCCAGGCCGCGGCCCAGCTGACCCTCGGGGCTCCCC60                CGGCAGCGGACAGGGAAGGGTTAAAGGCCCCCGGCTCCCTGCCCCCTGCCCTGGGGAACC120               CCTGGCCCTGTGGGGACATGAACTGTGTTTGCCGCCTGGTCCTGGTCGTG170                         MetAsnCysValCysArgLeuValLeuValVal                                             1510                                                                          CTGAGCCTGTGGCCAGATACAGCTGTCGCCCCTGGGCCACCACCTGGC218                           LeuSerLeuTrpProAspThrAlaValAlaProGlyProProProGly                              152025                                                                        CCCCCTCGAGTTTCCCCAGACCCTCGGGCCGAGCTGGACAGCACCGTG266                           ProProArgValSerProAspProArgAlaGluLeuAspSerThrVal                              303540                                                                        CTCCTGACCCGCTCTCTCCTGGCGGACACGCGGCAGCTGGCTGCACAG314                           LeuLeuThrArgSerLeuLeuAlaAspThrArgGlnLeuAlaAlaGln                              455055                                                                        CTGAGGGACAAATTCCCAGCTGACGGGGACCACAACCTGGATTCCCTG362                           LeuArgAspLysPheProAlaAspGlyAspHisAsnLeuAspSerLeu                              60657075                                                                      CCCACCCTGGCCATGAGTGCGGGGGCACTGGGAGCTCTACAGCTCCCA410                           ProThrLeuAlaMetSerAlaGlyAlaLeuGlyAlaLeuGlnLeuPro                              808590                                                                        GGTGTGCTGACAAGGCTGCGAGCGGACCTACTGTCCTACCTGCGGCAC458                           GlyValLeuThrArgLeuArgAlaAspLeuLeuSerTyrLeuArgHis                              95100105                                                                      GTGCAGTGGCTGCGCCGGGCAGGTGGCTCTTCCCTGAAGACCCTGGAG506                           ValGlnTrpLeuArgArgAlaGlyGlySerSerLeuLysThrLeuGlu                              110115120                                                                     CCCGAGCTGGGCACCCTGCAGGCCCGACTGGACCGGCTGCTGCGCCGG554                           ProGluLeuGlyThrLeuGlnAlaArgLeuAspArgLeuLeuArgArg                              125130135                                                                     CTGCAGCTCCTGATGTCCCGCCTGGCCCTGCCCCAGCCACCCCCGGAC602                           LeuGlnLeuLeuMetSerArgLeuAlaLeuProGlnProProProAsp                              140145150155                                                                  CCGCCGGCGCCCCCGCTGGCGCCCCCCTCCTCAGCCTGGGGGGGCATC650                           ProProAlaProProLeuAlaProProSerSerAlaTrpGlyGlyIle                              160165170                                                                     AGGGCCGCCCACGCCATCCTGGGGGGGCTGCACCTGACACTTGACTGG698                           ArgAlaAlaHisAlaIleLeuGlyGlyLeuHisLeuThrLeuAspTrp                              175180185                                                                     GCCGTGAGGGGACTGCTGCTGCTGAAGACTCGGCTGTGACCCGGGG744                             AlaValArgGlyLeuLeuLeuLeuLysThrArgLeu                                          190195                                                                        CCCAAAGCCACCACCGTCCTTCCAAAGCCAGATCTTATTTATTTATTTATTTCAGTACTG804               GGGGCGAAACAGCCAGGTGATCCCCCCGCCATTATCTCCCCCTAGTTAGAGACAGTCCTT864               CCGTGAGGCCTGGGGGACATCTGTGCCTTATTTATACTTATTTATTTCAGGAGCAGGGGT924               GGGAGGCAGGTGGACTCCTGGGTCCCCGAGGAGGAGGGGACTGGGGTCCCGGATTCTTGG984               GTCTCCAAGAAGTCTGTCCACAGACTTCTGCCCTGGCTCTTCCCCATCTAGGCCTGGGCA1044              GGAACATATATTATTTATTTAAGCAATTACTTTTCATGTTGGGGTGGGGACGGAGGGGAA1104              AGGGAAGCCTGGGTTTTTGTACAAAAATGTGAGAAACCTTTGTGAGACAGAGAACAGGGA1164              ATTAAATGTGTCATACATATCCAAAAAAAAAAAAAAAAAAAAAA1208                              (2) INFORMATION FOR SEQ ID NO:4:                                              (i) SEQUENCE CHARACTERISTICS:                                                 (A) LENGTH: 199 amino acids                                                   (B) TYPE: amino acid                                                          (D) TOPOLOGY: linear                                                          (ii) MOLECULE TYPE: protein                                                   (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:                                       MetAsnCysValCysArgLeuValLeuValValLeuSerLeuTrpPro                              151015                                                                        AspThrAlaValAlaProGlyProProProGlyProProArgValSer                              202530                                                                        ProAspProArgAlaGluLeuAspSerThrValLeuLeuThrArgSer                              354045                                                                        LeuLeuAlaAspThrArgGlnLeuAlaAlaGlnLeuArgAspLysPhe                              505560                                                                        ProAlaAspGlyAspHisAsnLeuAspSerLeuProThrLeuAlaMet                              65707580                                                                      SerAlaGlyAlaLeuGlyAlaLeuGlnLeuProGlyValLeuThrArg                              859095                                                                        LeuArgAlaAspLeuLeuSerTyrLeuArgHisValGlnTrpLeuArg                              100105110                                                                     ArgAlaGlyGlySerSerLeuLysThrLeuGluProGluLeuGlyThr                              115120125                                                                     LeuGlnAlaArgLeuAspArgLeuLeuArgArgLeuGlnLeuLeuMet                              130135140                                                                     SerArgLeuAlaLeuProGlnProProProAspProProAlaProPro                              145150155160                                                                  LeuAlaProProSerSerAlaTrpGlyGlyIleArgAlaAlaHisAla                              165170175                                                                     IleLeuGlyGlyLeuHisLeuThrLeuAspTrpAlaValArgGlyLeu                              180185190                                                                     LeuLeuLeuLysThrArgLeu                                                         195                                                                           __________________________________________________________________________

We claim:
 1. An isolated IL-11 having the amino acid sequence of SEQ IDNO: 2 and having one or more of the following characteristics:(1) anapparent molecular weight under reducing conditions on SDS PAGE ofapproximately 20 kd; (2) a calculated molecular weight of approximately20 kd; (3) biological activity in a T1165 assay; (4) biological activityin a megakaryocyte colony forming assay in the presence of IL-3; (5)biological activity on a B cell plaque forming assay.
 2. An isolatedmammalian IL-11 comprising amino acids 22-199 of SEQ ID NO:
 2. 3. AnIL-11 of claim 2 comprising the human sequence.
 4. An IL-11 of claim 2produced by culturing a cell transformed with a DNA sequence encodingexpression of said IL-11 polypeptide in operative association with anexpression control sequence capable of directing the replication andexpression of said IL-11, and recovering from the conditioned mediumthereof said IL-11 protein.
 5. A process for producing a mammalian IL-11comprising culturing a cell line transformed with a cDNA sequenceencoding a mammalian IL-11 of claim 2 in operative association with anexpression control sequence capable of directing the replication andexpression of said IL-11.
 6. An isolated DNA coding for an IL-11 ofclaim
 2. 7. A cell transformed with a DNA of claim 6 in operativeassociation with an expression control.
 8. A cell according to claim 7comprising a mammalian or bacterial cell.
 9. A plasmid vector comprisinga DNA of claim
 6. 10. A pharmaceutical composition comprising amammalian IL-11 of claim 2 in a pharmaceutically effective vehicle. 11.Homogeneous mammalian IL-11 of claim 2 having biological activity in theT1165 assay in the absence of IL-6.
 12. A method for increasing plateletformation comprising administering an effective amount of IL-11 of claim2.
 13. The method of claim 12, wherein said IL-11 is administeredintravenously.
 14. An injectable pharmaceutical composition forincreasing platelet formation comprising an aqueous solution of IL-11 ofclaim 2 and a pharmaceutically acceptable carrier.
 15. A DNA whichhybridizes under stringent conditions of 0.1 x SSC at 65° C. to a DNA ofclaim 6.